34ec4b4e44
Following up from #5730, replace some explicit matching over branch instructions with a use of inst_predicates::visit_block_succs.
831 lines
32 KiB
Rust
831 lines
32 KiB
Rust
//! A Dominator Tree represented as mappings of Blocks to their immediate dominator.
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use crate::entity::SecondaryMap;
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use crate::flowgraph::{BlockPredecessor, ControlFlowGraph};
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use crate::inst_predicates;
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use crate::ir::{Block, ExpandedProgramPoint, Function, Inst, Layout, ProgramOrder, Value};
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use crate::packed_option::PackedOption;
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use crate::timing;
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use alloc::vec::Vec;
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use core::cmp;
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use core::cmp::Ordering;
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use core::mem;
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/// RPO numbers are not first assigned in a contiguous way but as multiples of STRIDE, to leave
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/// room for modifications of the dominator tree.
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const STRIDE: u32 = 4;
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/// Special RPO numbers used during `compute_postorder`.
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const DONE: u32 = 1;
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const SEEN: u32 = 2;
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/// Dominator tree node. We keep one of these per block.
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#[derive(Clone, Default)]
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struct DomNode {
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/// Number of this node in a reverse post-order traversal of the CFG, starting from 1.
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/// This number is monotonic in the reverse postorder but not contiguous, since we leave
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/// holes for later localized modifications of the dominator tree.
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/// Unreachable nodes get number 0, all others are positive.
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rpo_number: u32,
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/// The immediate dominator of this block, represented as the branch or jump instruction at the
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/// end of the dominating basic block.
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///
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/// This is `None` for unreachable blocks and the entry block which doesn't have an immediate
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/// dominator.
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idom: PackedOption<Inst>,
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}
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/// The dominator tree for a single function.
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pub struct DominatorTree {
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nodes: SecondaryMap<Block, DomNode>,
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/// CFG post-order of all reachable blocks.
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postorder: Vec<Block>,
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/// Scratch memory used by `compute_postorder()`.
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stack: Vec<Block>,
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valid: bool,
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}
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/// Methods for querying the dominator tree.
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impl DominatorTree {
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/// Is `block` reachable from the entry block?
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pub fn is_reachable(&self, block: Block) -> bool {
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self.nodes[block].rpo_number != 0
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}
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/// Get the CFG post-order of blocks that was used to compute the dominator tree.
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///
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/// Note that this post-order is not updated automatically when the CFG is modified. It is
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/// computed from scratch and cached by `compute()`.
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pub fn cfg_postorder(&self) -> &[Block] {
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debug_assert!(self.is_valid());
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&self.postorder
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}
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/// Returns the immediate dominator of `block`.
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///
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/// The immediate dominator of a basic block is a basic block which we represent by
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/// the branch or jump instruction at the end of the basic block. This does not have to be the
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/// terminator of its block.
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///
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/// A branch or jump is said to *dominate* `block` if all control flow paths from the function
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/// entry to `block` must go through the branch.
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///
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/// The *immediate dominator* is the dominator that is closest to `block`. All other dominators
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/// also dominate the immediate dominator.
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///
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/// This returns `None` if `block` is not reachable from the entry block, or if it is the entry block
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/// which has no dominators.
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pub fn idom(&self, block: Block) -> Option<Inst> {
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self.nodes[block].idom.into()
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}
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/// Compare two blocks relative to the reverse post-order.
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fn rpo_cmp_block(&self, a: Block, b: Block) -> Ordering {
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self.nodes[a].rpo_number.cmp(&self.nodes[b].rpo_number)
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}
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/// Compare two program points relative to a reverse post-order traversal of the control-flow
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/// graph.
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///
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/// Return `Ordering::Less` if `a` comes before `b` in the RPO.
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///
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/// If `a` and `b` belong to the same block, compare their relative position in the block.
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pub fn rpo_cmp<A, B>(&self, a: A, b: B, layout: &Layout) -> Ordering
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where
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A: Into<ExpandedProgramPoint>,
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B: Into<ExpandedProgramPoint>,
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{
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let a = a.into();
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let b = b.into();
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self.rpo_cmp_block(layout.pp_block(a), layout.pp_block(b))
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.then(layout.cmp(a, b))
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}
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/// Returns `true` if `a` dominates `b`.
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///
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/// This means that every control-flow path from the function entry to `b` must go through `a`.
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///
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/// Dominance is ill defined for unreachable blocks. This function can always determine
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/// dominance for instructions in the same block, but otherwise returns `false` if either block
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/// is unreachable.
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///
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/// An instruction is considered to dominate itself.
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pub fn dominates<A, B>(&self, a: A, b: B, layout: &Layout) -> bool
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where
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A: Into<ExpandedProgramPoint>,
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B: Into<ExpandedProgramPoint>,
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{
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let a = a.into();
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let b = b.into();
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match a {
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ExpandedProgramPoint::Block(block_a) => {
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a == b || self.last_dominator(block_a, b, layout).is_some()
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}
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ExpandedProgramPoint::Inst(inst_a) => {
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let block_a = layout
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.inst_block(inst_a)
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.expect("Instruction not in layout.");
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match self.last_dominator(block_a, b, layout) {
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Some(last) => layout.cmp(inst_a, last) != Ordering::Greater,
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None => false,
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}
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}
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}
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}
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/// Find the last instruction in `a` that dominates `b`.
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/// If no instructions in `a` dominate `b`, return `None`.
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pub fn last_dominator<B>(&self, a: Block, b: B, layout: &Layout) -> Option<Inst>
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where
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B: Into<ExpandedProgramPoint>,
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{
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let (mut block_b, mut inst_b) = match b.into() {
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ExpandedProgramPoint::Block(block) => (block, None),
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ExpandedProgramPoint::Inst(inst) => (
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layout.inst_block(inst).expect("Instruction not in layout."),
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Some(inst),
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),
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};
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let rpo_a = self.nodes[a].rpo_number;
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// Run a finger up the dominator tree from b until we see a.
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// Do nothing if b is unreachable.
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while rpo_a < self.nodes[block_b].rpo_number {
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let idom = match self.idom(block_b) {
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Some(idom) => idom,
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None => return None, // a is unreachable, so we climbed past the entry
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};
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block_b = layout.inst_block(idom).expect("Dominator got removed.");
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inst_b = Some(idom);
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}
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if a == block_b {
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inst_b
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} else {
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None
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}
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}
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/// Compute the common dominator of two basic blocks.
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///
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/// Both basic blocks are assumed to be reachable.
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pub fn common_dominator(
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&self,
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mut a: BlockPredecessor,
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mut b: BlockPredecessor,
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layout: &Layout,
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) -> BlockPredecessor {
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loop {
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match self.rpo_cmp_block(a.block, b.block) {
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Ordering::Less => {
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// `a` comes before `b` in the RPO. Move `b` up.
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let idom = self.nodes[b.block].idom.expect("Unreachable basic block?");
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b = BlockPredecessor::new(
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layout.inst_block(idom).expect("Dangling idom instruction"),
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idom,
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);
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}
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Ordering::Greater => {
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// `b` comes before `a` in the RPO. Move `a` up.
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let idom = self.nodes[a.block].idom.expect("Unreachable basic block?");
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a = BlockPredecessor::new(
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layout.inst_block(idom).expect("Dangling idom instruction"),
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idom,
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);
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}
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Ordering::Equal => break,
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}
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}
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debug_assert_eq!(
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a.block, b.block,
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"Unreachable block passed to common_dominator?"
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);
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// We're in the same block. The common dominator is the earlier instruction.
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if layout.cmp(a.inst, b.inst) == Ordering::Less {
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a
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} else {
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b
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}
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}
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}
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impl DominatorTree {
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/// Allocate a new blank dominator tree. Use `compute` to compute the dominator tree for a
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/// function.
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pub fn new() -> Self {
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Self {
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nodes: SecondaryMap::new(),
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postorder: Vec::new(),
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stack: Vec::new(),
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valid: false,
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}
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}
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/// Allocate and compute a dominator tree.
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pub fn with_function(func: &Function, cfg: &ControlFlowGraph) -> Self {
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let block_capacity = func.layout.block_capacity();
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let mut domtree = Self {
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nodes: SecondaryMap::with_capacity(block_capacity),
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postorder: Vec::with_capacity(block_capacity),
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stack: Vec::new(),
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valid: false,
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};
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domtree.compute(func, cfg);
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domtree
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}
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/// Reset and compute a CFG post-order and dominator tree.
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pub fn compute(&mut self, func: &Function, cfg: &ControlFlowGraph) {
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let _tt = timing::domtree();
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debug_assert!(cfg.is_valid());
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self.compute_postorder(func);
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self.compute_domtree(func, cfg);
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self.valid = true;
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}
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/// Clear the data structures used to represent the dominator tree. This will leave the tree in
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/// a state where `is_valid()` returns false.
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pub fn clear(&mut self) {
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self.nodes.clear();
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self.postorder.clear();
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debug_assert!(self.stack.is_empty());
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self.valid = false;
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}
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/// Check if the dominator tree is in a valid state.
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///
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/// Note that this doesn't perform any kind of validity checks. It simply checks if the
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/// `compute()` method has been called since the last `clear()`. It does not check that the
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/// dominator tree is consistent with the CFG.
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pub fn is_valid(&self) -> bool {
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self.valid
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}
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/// Reset all internal data structures and compute a post-order of the control flow graph.
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///
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/// This leaves `rpo_number == 1` for all reachable blocks, 0 for unreachable ones.
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fn compute_postorder(&mut self, func: &Function) {
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self.clear();
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self.nodes.resize(func.dfg.num_blocks());
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// This algorithm is a depth first traversal (DFT) of the control flow graph, computing a
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// post-order of the blocks that are reachable form the entry block. A DFT post-order is not
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// unique. The specific order we get is controlled by two factors:
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//
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// 1. The order each node's children are visited, and
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// 2. The method used for pruning graph edges to get a tree.
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//
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// There are two ways of viewing the CFG as a graph:
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//
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// 1. Each block is a node, with outgoing edges for all the branches in the block.
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// 2. Each basic block is a node, with outgoing edges for the single branch at the end of
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// the BB. (A block is a linear sequence of basic blocks).
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//
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// The first graph is a contraction of the second one. We want to compute a block post-order
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// that is compatible both graph interpretations. That is, if you compute a BB post-order
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// and then remove those BBs that do not correspond to block headers, you get a post-order of
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// the block graph.
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//
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// Node child order:
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//
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// In the BB graph, we always go down the fall-through path first and follow the branch
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// destination second.
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//
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// In the block graph, this is equivalent to visiting block successors in a bottom-up
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// order, starting from the destination of the block's terminating jump, ending at the
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// destination of the first branch in the block.
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//
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// Edge pruning:
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//
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// In the BB graph, we keep an edge to a block the first time we visit the *source* side
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// of the edge. Any subsequent edges to the same block are pruned.
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//
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// The equivalent tree is reached in the block graph by keeping the first edge to a block
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// in a top-down traversal of the successors. (And then visiting edges in a bottom-up
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// order).
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//
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// This pruning method makes it possible to compute the DFT without storing lots of
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// information about the progress through a block.
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// During this algorithm only, use `rpo_number` to hold the following state:
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//
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// 0: block has not yet been reached in the pre-order.
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// SEEN: block has been pushed on the stack but successors not yet pushed.
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// DONE: Successors pushed.
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match func.layout.entry_block() {
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Some(block) => {
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self.stack.push(block);
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self.nodes[block].rpo_number = SEEN;
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}
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None => return,
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}
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while let Some(block) = self.stack.pop() {
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match self.nodes[block].rpo_number {
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SEEN => {
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// This is the first time we pop the block, so we need to scan its successors and
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// then revisit it.
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self.nodes[block].rpo_number = DONE;
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self.stack.push(block);
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self.push_successors(func, block);
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}
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DONE => {
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// This is the second time we pop the block, so all successors have been
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// processed.
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self.postorder.push(block);
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}
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_ => unreachable!(),
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}
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}
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}
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/// Push `block` successors onto `self.stack`, filtering out those that have already been seen.
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///
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/// The successors are pushed in program order which is important to get a split-invariant
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/// post-order. Split-invariant means that if a block is split in two, we get the same
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/// post-order except for the insertion of the new block header at the split point.
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fn push_successors(&mut self, func: &Function, block: Block) {
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inst_predicates::visit_block_succs(func, block, |_, succ, _| self.push_if_unseen(succ))
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}
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/// Push `block` onto `self.stack` if it has not already been seen.
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fn push_if_unseen(&mut self, block: Block) {
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if self.nodes[block].rpo_number == 0 {
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self.nodes[block].rpo_number = SEEN;
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self.stack.push(block);
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}
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}
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/// Build a dominator tree from a control flow graph using Keith D. Cooper's
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/// "Simple, Fast Dominator Algorithm."
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fn compute_domtree(&mut self, func: &Function, cfg: &ControlFlowGraph) {
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// During this algorithm, `rpo_number` has the following values:
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//
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// 0: block is not reachable.
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// 1: block is reachable, but has not yet been visited during the first pass. This is set by
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// `compute_postorder`.
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// 2+: block is reachable and has an assigned RPO number.
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// We'll be iterating over a reverse post-order of the CFG, skipping the entry block.
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let (entry_block, postorder) = match self.postorder.as_slice().split_last() {
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Some((&eb, rest)) => (eb, rest),
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None => return,
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};
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debug_assert_eq!(Some(entry_block), func.layout.entry_block());
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// Do a first pass where we assign RPO numbers to all reachable nodes.
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self.nodes[entry_block].rpo_number = 2 * STRIDE;
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for (rpo_idx, &block) in postorder.iter().rev().enumerate() {
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// Update the current node and give it an RPO number.
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// The entry block got 2, the rest start at 3 by multiples of STRIDE to leave
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// room for future dominator tree modifications.
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//
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// Since `compute_idom` will only look at nodes with an assigned RPO number, the
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// function will never see an uninitialized predecessor.
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//
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// Due to the nature of the post-order traversal, every node we visit will have at
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// least one predecessor that has previously been visited during this RPO.
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self.nodes[block] = DomNode {
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idom: self.compute_idom(block, cfg, &func.layout).into(),
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rpo_number: (rpo_idx as u32 + 3) * STRIDE,
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}
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}
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// Now that we have RPO numbers for everything and initial immediate dominator estimates,
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// iterate until convergence.
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//
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// If the function is free of irreducible control flow, this will exit after one iteration.
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let mut changed = true;
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while changed {
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changed = false;
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for &block in postorder.iter().rev() {
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let idom = self.compute_idom(block, cfg, &func.layout).into();
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if self.nodes[block].idom != idom {
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self.nodes[block].idom = idom;
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changed = true;
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}
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}
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}
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}
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// Compute the immediate dominator for `block` using the current `idom` states for the reachable
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// nodes.
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fn compute_idom(&self, block: Block, cfg: &ControlFlowGraph, layout: &Layout) -> Inst {
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// Get an iterator with just the reachable, already visited predecessors to `block`.
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// Note that during the first pass, `rpo_number` is 1 for reachable blocks that haven't
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// been visited yet, 0 for unreachable blocks.
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let mut reachable_preds = cfg
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.pred_iter(block)
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.filter(|&BlockPredecessor { block: pred, .. }| self.nodes[pred].rpo_number > 1);
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// The RPO must visit at least one predecessor before this node.
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let mut idom = reachable_preds
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.next()
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.expect("block node must have one reachable predecessor");
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for pred in reachable_preds {
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idom = self.common_dominator(idom, pred, layout);
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}
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idom.inst
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}
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}
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/// Optional pre-order information that can be computed for a dominator tree.
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///
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/// This data structure is computed from a `DominatorTree` and provides:
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///
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/// - A forward traversable dominator tree through the `children()` iterator.
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/// - An ordering of blocks according to a dominator tree pre-order.
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/// - Constant time dominance checks at the block granularity.
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///
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/// The information in this auxiliary data structure is not easy to update when the control flow
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/// graph changes, which is why it is kept separate.
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pub struct DominatorTreePreorder {
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nodes: SecondaryMap<Block, ExtraNode>,
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// Scratch memory used by `compute_postorder()`.
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stack: Vec<Block>,
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}
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#[derive(Default, Clone)]
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struct ExtraNode {
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/// First child node in the domtree.
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child: PackedOption<Block>,
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/// Next sibling node in the domtree. This linked list is ordered according to the CFG RPO.
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sibling: PackedOption<Block>,
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/// Sequence number for this node in a pre-order traversal of the dominator tree.
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/// Unreachable blocks have number 0, the entry block is 1.
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pre_number: u32,
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/// Maximum `pre_number` for the sub-tree of the dominator tree that is rooted at this node.
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/// This is always >= `pre_number`.
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pre_max: u32,
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}
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/// Creating and computing the dominator tree pre-order.
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impl DominatorTreePreorder {
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/// Create a new blank `DominatorTreePreorder`.
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pub fn new() -> Self {
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Self {
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nodes: SecondaryMap::new(),
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stack: Vec::new(),
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}
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}
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/// Recompute this data structure to match `domtree`.
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|
pub fn compute(&mut self, domtree: &DominatorTree, layout: &Layout) {
|
|
self.nodes.clear();
|
|
debug_assert_eq!(self.stack.len(), 0);
|
|
|
|
// Step 1: Populate the child and sibling links.
|
|
//
|
|
// By following the CFG post-order and pushing to the front of the lists, we make sure that
|
|
// sibling lists are ordered according to the CFG reverse post-order.
|
|
for &block in domtree.cfg_postorder() {
|
|
if let Some(idom_inst) = domtree.idom(block) {
|
|
let idom = layout.pp_block(idom_inst);
|
|
let sib = mem::replace(&mut self.nodes[idom].child, block.into());
|
|
self.nodes[block].sibling = sib;
|
|
} else {
|
|
// The only block without an immediate dominator is the entry.
|
|
self.stack.push(block);
|
|
}
|
|
}
|
|
|
|
// Step 2. Assign pre-order numbers from a DFS of the dominator tree.
|
|
debug_assert!(self.stack.len() <= 1);
|
|
let mut n = 0;
|
|
while let Some(block) = self.stack.pop() {
|
|
n += 1;
|
|
let node = &mut self.nodes[block];
|
|
node.pre_number = n;
|
|
node.pre_max = n;
|
|
if let Some(n) = node.sibling.expand() {
|
|
self.stack.push(n);
|
|
}
|
|
if let Some(n) = node.child.expand() {
|
|
self.stack.push(n);
|
|
}
|
|
}
|
|
|
|
// Step 3. Propagate the `pre_max` numbers up the tree.
|
|
// The CFG post-order is topologically ordered w.r.t. dominance so a node comes after all
|
|
// its dominator tree children.
|
|
for &block in domtree.cfg_postorder() {
|
|
if let Some(idom_inst) = domtree.idom(block) {
|
|
let idom = layout.pp_block(idom_inst);
|
|
let pre_max = cmp::max(self.nodes[block].pre_max, self.nodes[idom].pre_max);
|
|
self.nodes[idom].pre_max = pre_max;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// An iterator that enumerates the direct children of a block in the dominator tree.
|
|
pub struct ChildIter<'a> {
|
|
dtpo: &'a DominatorTreePreorder,
|
|
next: PackedOption<Block>,
|
|
}
|
|
|
|
impl<'a> Iterator for ChildIter<'a> {
|
|
type Item = Block;
|
|
|
|
fn next(&mut self) -> Option<Block> {
|
|
let n = self.next.expand();
|
|
if let Some(block) = n {
|
|
self.next = self.dtpo.nodes[block].sibling;
|
|
}
|
|
n
|
|
}
|
|
}
|
|
|
|
/// Query interface for the dominator tree pre-order.
|
|
impl DominatorTreePreorder {
|
|
/// Get an iterator over the direct children of `block` in the dominator tree.
|
|
///
|
|
/// These are the block's whose immediate dominator is an instruction in `block`, ordered according
|
|
/// to the CFG reverse post-order.
|
|
pub fn children(&self, block: Block) -> ChildIter {
|
|
ChildIter {
|
|
dtpo: self,
|
|
next: self.nodes[block].child,
|
|
}
|
|
}
|
|
|
|
/// Fast, constant time dominance check with block granularity.
|
|
///
|
|
/// This computes the same result as `domtree.dominates(a, b)`, but in guaranteed fast constant
|
|
/// time. This is less general than the `DominatorTree` method because it only works with block
|
|
/// program points.
|
|
///
|
|
/// A block is considered to dominate itself.
|
|
pub fn dominates(&self, a: Block, b: Block) -> bool {
|
|
let na = &self.nodes[a];
|
|
let nb = &self.nodes[b];
|
|
na.pre_number <= nb.pre_number && na.pre_max >= nb.pre_max
|
|
}
|
|
|
|
/// Compare two blocks according to the dominator pre-order.
|
|
pub fn pre_cmp_block(&self, a: Block, b: Block) -> Ordering {
|
|
self.nodes[a].pre_number.cmp(&self.nodes[b].pre_number)
|
|
}
|
|
|
|
/// Compare two program points according to the dominator tree pre-order.
|
|
///
|
|
/// This ordering of program points have the property that given a program point, pp, all the
|
|
/// program points dominated by pp follow immediately and contiguously after pp in the order.
|
|
pub fn pre_cmp<A, B>(&self, a: A, b: B, layout: &Layout) -> Ordering
|
|
where
|
|
A: Into<ExpandedProgramPoint>,
|
|
B: Into<ExpandedProgramPoint>,
|
|
{
|
|
let a = a.into();
|
|
let b = b.into();
|
|
self.pre_cmp_block(layout.pp_block(a), layout.pp_block(b))
|
|
.then(layout.cmp(a, b))
|
|
}
|
|
|
|
/// Compare two value defs according to the dominator tree pre-order.
|
|
///
|
|
/// Two values defined at the same program point are compared according to their parameter or
|
|
/// result order.
|
|
///
|
|
/// This is a total ordering of the values in the function.
|
|
pub fn pre_cmp_def(&self, a: Value, b: Value, func: &Function) -> Ordering {
|
|
let da = func.dfg.value_def(a);
|
|
let db = func.dfg.value_def(b);
|
|
self.pre_cmp(da, db, &func.layout)
|
|
.then_with(|| da.num().cmp(&db.num()))
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
use crate::cursor::{Cursor, FuncCursor};
|
|
use crate::flowgraph::ControlFlowGraph;
|
|
use crate::ir::types::*;
|
|
use crate::ir::{Function, InstBuilder, TrapCode};
|
|
|
|
#[test]
|
|
fn empty() {
|
|
let func = Function::new();
|
|
let cfg = ControlFlowGraph::with_function(&func);
|
|
debug_assert!(cfg.is_valid());
|
|
let dtree = DominatorTree::with_function(&func, &cfg);
|
|
assert_eq!(0, dtree.nodes.keys().count());
|
|
assert_eq!(dtree.cfg_postorder(), &[]);
|
|
|
|
let mut dtpo = DominatorTreePreorder::new();
|
|
dtpo.compute(&dtree, &func.layout);
|
|
}
|
|
|
|
#[test]
|
|
fn unreachable_node() {
|
|
let mut func = Function::new();
|
|
let block0 = func.dfg.make_block();
|
|
let v0 = func.dfg.append_block_param(block0, I32);
|
|
let block1 = func.dfg.make_block();
|
|
let block2 = func.dfg.make_block();
|
|
let trap_block = func.dfg.make_block();
|
|
|
|
let mut cur = FuncCursor::new(&mut func);
|
|
|
|
cur.insert_block(block0);
|
|
cur.ins().brif(v0, block2, &[], trap_block, &[]);
|
|
|
|
cur.insert_block(trap_block);
|
|
cur.ins().trap(TrapCode::User(0));
|
|
|
|
cur.insert_block(block1);
|
|
let v1 = cur.ins().iconst(I32, 1);
|
|
let v2 = cur.ins().iadd(v0, v1);
|
|
cur.ins().jump(block0, &[v2]);
|
|
|
|
cur.insert_block(block2);
|
|
cur.ins().return_(&[v0]);
|
|
|
|
let cfg = ControlFlowGraph::with_function(cur.func);
|
|
let dt = DominatorTree::with_function(cur.func, &cfg);
|
|
|
|
// Fall-through-first, prune-at-source DFT:
|
|
//
|
|
// block0 {
|
|
// brif block2 {
|
|
// trap
|
|
// block2 {
|
|
// return
|
|
// } block2
|
|
// } block0
|
|
assert_eq!(dt.cfg_postorder(), &[trap_block, block2, block0]);
|
|
|
|
let v2_def = cur.func.dfg.value_def(v2).unwrap_inst();
|
|
assert!(!dt.dominates(v2_def, block0, &cur.func.layout));
|
|
assert!(!dt.dominates(block0, v2_def, &cur.func.layout));
|
|
|
|
let mut dtpo = DominatorTreePreorder::new();
|
|
dtpo.compute(&dt, &cur.func.layout);
|
|
assert!(dtpo.dominates(block0, block0));
|
|
assert!(!dtpo.dominates(block0, block1));
|
|
assert!(dtpo.dominates(block0, block2));
|
|
assert!(!dtpo.dominates(block1, block0));
|
|
assert!(dtpo.dominates(block1, block1));
|
|
assert!(!dtpo.dominates(block1, block2));
|
|
assert!(!dtpo.dominates(block2, block0));
|
|
assert!(!dtpo.dominates(block2, block1));
|
|
assert!(dtpo.dominates(block2, block2));
|
|
}
|
|
|
|
#[test]
|
|
fn non_zero_entry_block() {
|
|
let mut func = Function::new();
|
|
let block0 = func.dfg.make_block();
|
|
let block1 = func.dfg.make_block();
|
|
let block2 = func.dfg.make_block();
|
|
let block3 = func.dfg.make_block();
|
|
let cond = func.dfg.append_block_param(block3, I32);
|
|
|
|
let mut cur = FuncCursor::new(&mut func);
|
|
|
|
cur.insert_block(block3);
|
|
let jmp_block3_block1 = cur.ins().jump(block1, &[]);
|
|
|
|
cur.insert_block(block1);
|
|
let br_block1_block0_block2 = cur.ins().brif(cond, block0, &[], block2, &[]);
|
|
|
|
cur.insert_block(block2);
|
|
cur.ins().jump(block0, &[]);
|
|
|
|
cur.insert_block(block0);
|
|
|
|
let cfg = ControlFlowGraph::with_function(cur.func);
|
|
let dt = DominatorTree::with_function(cur.func, &cfg);
|
|
|
|
// Fall-through-first, prune-at-source DFT:
|
|
//
|
|
// block3 {
|
|
// block3:jump block1 {
|
|
// block1 {
|
|
// block1:brif block0 {
|
|
// block1:jump block2 {
|
|
// block2 {
|
|
// block2:jump block0 (seen)
|
|
// } block2
|
|
// } block1:jump block2
|
|
// block0 {
|
|
// } block0
|
|
// } block1:brif block0
|
|
// } block1
|
|
// } block3:jump block1
|
|
// } block3
|
|
|
|
assert_eq!(dt.cfg_postorder(), &[block2, block0, block1, block3]);
|
|
|
|
assert_eq!(cur.func.layout.entry_block().unwrap(), block3);
|
|
assert_eq!(dt.idom(block3), None);
|
|
assert_eq!(dt.idom(block1).unwrap(), jmp_block3_block1);
|
|
assert_eq!(dt.idom(block2).unwrap(), br_block1_block0_block2);
|
|
assert_eq!(dt.idom(block0).unwrap(), br_block1_block0_block2);
|
|
|
|
assert!(dt.dominates(
|
|
br_block1_block0_block2,
|
|
br_block1_block0_block2,
|
|
&cur.func.layout
|
|
));
|
|
assert!(!dt.dominates(br_block1_block0_block2, jmp_block3_block1, &cur.func.layout));
|
|
assert!(dt.dominates(jmp_block3_block1, br_block1_block0_block2, &cur.func.layout));
|
|
|
|
assert_eq!(
|
|
dt.rpo_cmp(block3, block3, &cur.func.layout),
|
|
Ordering::Equal
|
|
);
|
|
assert_eq!(dt.rpo_cmp(block3, block1, &cur.func.layout), Ordering::Less);
|
|
assert_eq!(
|
|
dt.rpo_cmp(block3, jmp_block3_block1, &cur.func.layout),
|
|
Ordering::Less
|
|
);
|
|
assert_eq!(
|
|
dt.rpo_cmp(jmp_block3_block1, br_block1_block0_block2, &cur.func.layout),
|
|
Ordering::Less
|
|
);
|
|
}
|
|
|
|
#[test]
|
|
fn backwards_layout() {
|
|
let mut func = Function::new();
|
|
let block0 = func.dfg.make_block();
|
|
let block1 = func.dfg.make_block();
|
|
let block2 = func.dfg.make_block();
|
|
|
|
let mut cur = FuncCursor::new(&mut func);
|
|
|
|
cur.insert_block(block0);
|
|
let jmp02 = cur.ins().jump(block2, &[]);
|
|
|
|
cur.insert_block(block1);
|
|
let trap = cur.ins().trap(TrapCode::User(5));
|
|
|
|
cur.insert_block(block2);
|
|
let jmp21 = cur.ins().jump(block1, &[]);
|
|
|
|
let cfg = ControlFlowGraph::with_function(cur.func);
|
|
let dt = DominatorTree::with_function(cur.func, &cfg);
|
|
|
|
assert_eq!(cur.func.layout.entry_block(), Some(block0));
|
|
assert_eq!(dt.idom(block0), None);
|
|
assert_eq!(dt.idom(block1), Some(jmp21));
|
|
assert_eq!(dt.idom(block2), Some(jmp02));
|
|
|
|
assert!(dt.dominates(block0, block0, &cur.func.layout));
|
|
assert!(dt.dominates(block0, jmp02, &cur.func.layout));
|
|
assert!(dt.dominates(block0, block1, &cur.func.layout));
|
|
assert!(dt.dominates(block0, trap, &cur.func.layout));
|
|
assert!(dt.dominates(block0, block2, &cur.func.layout));
|
|
assert!(dt.dominates(block0, jmp21, &cur.func.layout));
|
|
|
|
assert!(!dt.dominates(jmp02, block0, &cur.func.layout));
|
|
assert!(dt.dominates(jmp02, jmp02, &cur.func.layout));
|
|
assert!(dt.dominates(jmp02, block1, &cur.func.layout));
|
|
assert!(dt.dominates(jmp02, trap, &cur.func.layout));
|
|
assert!(dt.dominates(jmp02, block2, &cur.func.layout));
|
|
assert!(dt.dominates(jmp02, jmp21, &cur.func.layout));
|
|
|
|
assert!(!dt.dominates(block1, block0, &cur.func.layout));
|
|
assert!(!dt.dominates(block1, jmp02, &cur.func.layout));
|
|
assert!(dt.dominates(block1, block1, &cur.func.layout));
|
|
assert!(dt.dominates(block1, trap, &cur.func.layout));
|
|
assert!(!dt.dominates(block1, block2, &cur.func.layout));
|
|
assert!(!dt.dominates(block1, jmp21, &cur.func.layout));
|
|
|
|
assert!(!dt.dominates(trap, block0, &cur.func.layout));
|
|
assert!(!dt.dominates(trap, jmp02, &cur.func.layout));
|
|
assert!(!dt.dominates(trap, block1, &cur.func.layout));
|
|
assert!(dt.dominates(trap, trap, &cur.func.layout));
|
|
assert!(!dt.dominates(trap, block2, &cur.func.layout));
|
|
assert!(!dt.dominates(trap, jmp21, &cur.func.layout));
|
|
|
|
assert!(!dt.dominates(block2, block0, &cur.func.layout));
|
|
assert!(!dt.dominates(block2, jmp02, &cur.func.layout));
|
|
assert!(dt.dominates(block2, block1, &cur.func.layout));
|
|
assert!(dt.dominates(block2, trap, &cur.func.layout));
|
|
assert!(dt.dominates(block2, block2, &cur.func.layout));
|
|
assert!(dt.dominates(block2, jmp21, &cur.func.layout));
|
|
|
|
assert!(!dt.dominates(jmp21, block0, &cur.func.layout));
|
|
assert!(!dt.dominates(jmp21, jmp02, &cur.func.layout));
|
|
assert!(dt.dominates(jmp21, block1, &cur.func.layout));
|
|
assert!(dt.dominates(jmp21, trap, &cur.func.layout));
|
|
assert!(!dt.dominates(jmp21, block2, &cur.func.layout));
|
|
assert!(dt.dominates(jmp21, jmp21, &cur.func.layout));
|
|
}
|
|
}
|